Add pkg-config and remove stale comment

Dockerfile

@@ -3,9 +3,8 @@
 # as musl doesn't support cdylib
 FROM node:20-slim AS builder
 
-# Needed to build rust things for matrix-sdk-crypto-nodejs
-# See https://github.com/matrix-org/matrix-rust-sdk-bindings/blob/main/crates/matrix-sdk-crypto-nodejs/release/Dockerfile.linux#L5-L6
-RUN apt-get update && apt-get install -y build-essential cmake curl
+# Needed in order to build rust FFI bindings.
+RUN apt-get update && apt-get install -y build-essential cmake curl pkg-config
 
 RUN curl https://sh.rustup.rs -sSf | sh -s -- -y --profile minimal
 ENV PATH="/root/.cargo/bin:${PATH}"